OSV-2021-37 Heap-buffer-overflow in WelsDec::CopyRectBlock4Cols

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=29431 Crash type: Heap-buffer-overflow READ 16 Crash state: WelsDec::CopyRectBlock4Cols WelsDec::GetColocatedMb WelsDec::PredMvBDirectSpatial...